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 MIL-HDBK-232A
4.3.3.3 Facsimile devices. Facsimile devices are of two basic types, analog
and digital. Analog devices operate at a low speed and may require the use
of an analog-to-digital converter to produce a digitized line signal that may
be encrypted. New technology facsimile devices use digital signaling and do
not require signal conversion prior to encryption. For either type, the
principle RED/ BLACK installation practices include shielding, filtering,
separation, and isolation.
4.3.3.4 Video devices. Video devices as RED processors are typically used
in an area where the entire video distribution is among closely associated
spaces within a single building or a small group of buildings. It is
desirable to provide a protected distribution system (PDS) with the signals
transmitted over one or more fiber optic cables (FOCs) within the PDS,
thereby reducing the TEMPEST vulnerability of the system. (See NACSIM 4009.)
However, the use of appropriate grounding, bonding, and shielding (CBS) for
all wire lines within the system is still required. Some video devices may
wire-line conduction between units. This requires that the signal be
digitized and encrypted while in its baseband form. Remember, CBS is
critical for this type of system.
4.3.3.5 Computers. This category includes a wide variety of devices from a
microcomputer used as a word processor in a stand alone configuration to a
large multicomponent, multiprocessing system which connects to varied types
of terminals. Examples include moderate sized RED digital computerized
telephone switches serving local areas, intrafacility computer networks with
numerous work stations, or computer-aided design systems used for producing
sensitive or classified drawings.
4.3.3.6 Ancillary devices. This category includes devices such as analog to
digital/digital-to-analog converters, line controller units, crypto-bypass
devices, line drivers, rate converters, rate buffers, synchronizers, and any
other unit required between the user terminal and the encryption device. The
common characteristic of an ancillary device is that it may be RED on both
input and output and may not require any human attention during operation.
4.3.3.7 Storage devices. This category includes both on-line and off-line
devices since the RED/ BLACK considerations are the same for both. It also
includes any device in which classified information is stored in other than
hard copy form, such as magnetic tape recorders/reproducers, magnetic disk,
drum or card recorders/reproducers, and computer memories (magnetic or
electronic).
4.3.4 Local area networks (LANs). When a LAN is designed or proposed for
the purpose of processing classified information, the topology of the LAN
must be determined in order to establish the protective measures required.
Two topologies exist -- point-to-point and multipoint (may be called
multipath or bus technology). Each requires different protection
Additionally, the transmission media between LAN nodes becomes a significant
issue in defining the topology.
4.3.4.1 Point-to-point topology. A point-to-point topology is characterized
by dedicated paths between any two nodes. The paths are not shared (see
figure 4). A point-to-point network may consist of any number of nodes.
Each path will interconnect only two nodes. A node must have a path to a
node with which it wishes to communicate. or must he switched through another
node. This topology lends itself to being designed and installed using
existing cryptographic devices to secure each path. Each node is installed
using the RED/BLACK concepts defined in this handbook. Figures 5 and 6
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